1. Field of the Invention
The present invention relates to an apparatus useful in generating and counting aerosol particles. In particular, the invention relates to an apparatus which is capable of generating and counting low concentrations of individual aerosol particles.
2. Description of the Prior Art
Recently, governments have become increasingly interested in identifying and controlling developed biological warfare agents. These agents are highly dangerous and extreme caution must be used in the handling of these agents. In the event that these agents are deployed, part of the initial defense includes the rapid and accurate detection of the agents.
Instruments which are used to detect biological warfare agents include apparatus which analyze aerosols such as the CB mass spectrometer or a UV fluorescence-based detector. The instruments must be properly calibrated before being employed. Calibration of these instruments requires the use of aerosol particles that are agglomerates of individual bacteria cells or spores. In the past, the aerosolized particles, nebulizers, sprayers fluidized beds, sonic nozzles, etc. have been used. These apparatus, however, produce copious amounts of aerosols which may have a more or less compact size distribution depending upon the specific technique used to generate the aerosol. Measuring the amount of individual aerosol particles generated is often difficult and usually only approximated. In fact, the aerosols are measured by the mass of the material consumed by the apparatus rather than the actual amount of aerosol particles generated. In addition, although there are currently available scientific droplet generators capable of forming droplets of a uniform size such as the Vibrating Orifice Aerosol Generator (TSI Inc, Minneapolis, Minn.), they are not, however, suitable for the calibration needs described above. Such devices are of a high speed free-running nature and do not allow exact counts of small numbers of aerosol particles made.
In view of the need to more accurately calibrate biological warfare detection apparatus, there is a need for improved aerosol generating apparatus. In particular, there is a need for an apparatus which allows an investigator to control the amount, size and rate of generation of aerosol particles. There is also a need in this field to provide a means of delivering aerosol particles in a low velocity air-stream which is suitable for direct injection into analyzing instruments. Then present invention addresses these needs.